Wind energy conversion apparatus

ABSTRACT

A wind energy conversion apparatus comprising a supporting structure is presented. The apparatus further comprises shaft having a first and a second end, which is rotatably journalled in said supporting structure, as well as at least one rotor blade having a first end and a second end, which rotor blade is mounted on said shaft with both ends. The object of the presented wind energy conversion apparatus is to improve the known apparatus and to provide an apparatus which is capable of converting a larger amount of wind energy into other forms of energy. Accordingly wind energy conversion apparatus according to the invention is to that end characterized in that the rotor blade is provided with additional wind capturing means.

The invention relates to a wind energy conversion apparatus comprising a supporting structure; a shaft having a first and a second end, which is rotatably Journalled in said supporting structure, as well as at least one rotor blade having a first end and a second end, which rotor blade is mounted on said shaft with both ends.

The invention also relates to a rotor blade for use in such wind energy conversion apparatus.

Wind energy conversion apparatuses of the kind referred to above are already known from German patent publication No. 3331166 A. The horizontal shaft thereby extends in the direction of the oncoming wind, all this in such a manner that the plane of inflow of said wind capturing means extends substantially perpendicularly to the main shaft and also substantially perpendicularly to the direction of the oncoming wind.

For a long time already people have attempted to convert an increasing amount of wind energy into other forms of energy. It is known that this can be achieved by enlarging the area that is covered by the rotating rotor blade. This enlargement can be accomplished by using rotor blades having a greater length. Such longer rotor blades are expensive as regards their construction, however, because they must also be capable of taking up flexural stress induced by the wind and by gyroscopic effects. The length of such a rotor blade is limited by the large mechanical forces to which such long rotor blades are subjected. In addition, such long rotor blades cause the noise level to increase, which renders the use of such wind turbines in built-up areas less desirable.

The object of the invention is to improve the known apparatus and to provide a wind energy conversion apparatus which, given the same dimensions and the same wind conditions, is capable of converting a larger amount of wind energy into other forms of energy. In order to accomplish that objective, the wind energy conversion apparatus according to the invention is characterized in that the rotor blade is provided with additional wind capturing means.

As a result of the special construction of the rotor blade that is used in the apparatus, the windward side of the rotor blade, in addition to exerting a force in the direction of the air flow, also exerts a force on the air flow in radial direction, which results in a Venturi effect. Said Venturi effect leads to an increased flow of air through the rotor, enabling the wind energy conversion apparatus according to the invention to draw more energy from the air flowing through the apparatus. This results in the significantly improved efficiency of the apparatus according to the invention.

The wind capturing means may consist of a widened portion of the rotor blade, which widened portion is circular in shape in one embodiment and ellipsoidal in shape in another embodiment. It has become apparent that the Venturi effect is enhanced when the rotor blade is provided with additional wind capturing means as explained above. As a result, even more air will flow through the area covered by the rotor blade, so that the wind energy conversion apparatus can draw energy from the wind in a more efficient manner.

Such a wind conversion apparatus according to the invention is thus characterized by its simple but nevertheless robust construction, since the rotor blade is only subjected to tensile stress during operation when this construction is used. Since the rotor blade does not have a tip, in contrast to the known windmills or wind turbines, the noise production of a wind energy conversion apparatus according to the invention is furthermore significantly lower than that of the current apparatus. This renders the wind energy conversion apparatus according to the invention quite suitable for use in built-up areas.

More in particular, the two ends of the rotor blade are according to the invention mounted some distance apart on the shaft.

It has been established by experiment that the wind energy conversion apparatus according to the invention is very effective in drawing energy from the air flowing through and around the apparatus when the spacing between the two ends equals about twice the radius of the rotor blade.

In a specific embodiment of the invention, the rotor blade is elongate in shape, in a special embodiment it is embodied as a thin, flat plate.

According to the invention, the rotor blade is made of a metal or of a synthetic fibre material. In combination with the configuration of the rotor blade as a thin, flat plate, the rotor blade according to the invention can be mass-produced at low cost in a quick and simple manner. Since the cost price of a wind energy conversion apparatus is to a large extent determined by the construction costs of the rotor blade, the wind energy conversion apparatus according to the invention can in addition be produced at significantly lower cost due to said significant reduction of the manufacturing costs of rotor blades according to the invention. This offers greater possibilities of installing relatively small wind energy conversion apparatuses according to the invention in built-up-up areas, for example on the property of private individuals, so that the acceptation level of such a wind energy conversion apparatus will be considerably higher.

In a very specific embodiment, the wind energy conversion apparatus according to the invention comprises two or more rotor blades mounted on the shaft, which rotor blades describe mutually different diameters.

In one embodiment of the apparatus, the two ends of the rotor blade are each mounted near a corresponding end of the shaft, with the shaft being mounted in bearings in the supporting structure with both its ends. This construction makes it possible to obtain an efficient rotor (a horizontal shaft with one or more rotor blades mounted thereon) while using a compact construction, which rotor draws energy from the air flowing through and around the apparatus in a very efficient manner.

According to the invention, in order to achieve an effective conversion of the wind energy into electrical energy, the shaft is coupled with means, such as a generator, for converting rotational energy into electrical energy. Said generator may be mounted in or on the bearing-mounted shaft.

The invention also relates to a rotor blade according to the invention as described in the description of the figures and as shown in the drawings.

The invention will now be explained in more detail with reference to the drawings, in which:

FIG. 1 schematically shows an embodiment of a prior art wind energy conversion apparatus;

FIGS. 2A-2B is a detail view of the wind energy conversion apparatus that is shown in FIG. 1;

FIGS. 3A-3B show an embodiment of a rotor blade for use in a wind energy conversion apparatus according to the invention; and

FIG. 4 shows a second embodiment of a wind energy conversion apparatus according to the invention.

A prior art wind energy conversion apparatus according to the invention will now be described with reference to FIG. 1. For the sake of completeness, corresponding parts are indicated by the same numerals.

The wind energy conversion apparatus 1 that is shown in FIG. 1 comprises a vertical column 2 a, on which a supporting structure 2 b is mounted. In the supporting structure 2 b, a horizontal shaft 3 is rotatably accommodated with its first end 3 a and its second end 3 b in bearings 2 c and 2 d, respectively, which form part of the supporting structure 2 b. The wind energy conversion apparatus 1 is provided with one rotor blade, two rotor blades 4-4′ in this embodiment, which rotor blades 4-4′ are fixedly connected to the horizontal shaft 3 with their first end 4 a-4 a′ and their second end 4 b-4 b′.

An angular displacement in the two ends of the rotor blade of the wind energy conversion apparatus will cause the apparatus to start rotating of Its own accord, i.e. no additional energy source is required for setting the rotor blades in motion, after which the wind will take over the rotor blade drive. Furthermore, the wind energy conversion apparatus aligns itself with the oncoming wind, because the rotor functions as a windvane during rotation. The supporting structure 2 b is rotatably mounted on the vertical column 2 a by means of a rotation bearing 8.

Preferably, a windvane is mounted, so that the wind energy conversion apparatus will align itself with the wind even at very low wind velocities. Thus the wind energy conversion apparatus as shown in, FIG. 1 will invariably align Itself with the wind in such a manner that the horizontal shaft 3 will extend in the direction of the wind at all times, as is indicated by the arrow in FIG. 1.

As is shown in FIG. 1, the two ends 4 a-4 a′ and 4 b-4 b′, respectively, of the rotor blades 4-4′ are according to the invention mounted on the horizontal shaft 3 with a spacing b between them; in a specific embodiment, the spacing b between the two ends 4 a-4 a′ and 4 b-4 b′, respectively, of the rotor blades 4-4′ amounts to less than twice the radius R of each rotor blade 4-4′.

In another embodiment, said spacing b may amount to twice the radius R, and in yet another embodiment said spacing 2 b may amount to more than twice the radius R of the rotor blade 4-4′. Twice the radius R of the rotor blade corresponds to the diameter D that the rotor blade describes in the air during operation.

As is clearly shown in FIG. 1, the two ends 4 a-4 a′ and 4 b-4 b′, respectively, of the rotor blades 4-4′ are disposed near the first end 3 a and the second end 3 b, respectively, of the horizontal shaft 3.

As a result of the relatively simple construction of the wind energy conversion apparatus according to FIG. 1, the only stress that occurs in the rotor blades 4-4′ once the wind has set the rotors going is tensile stress, which makes it possible to use a simple construction for the rotor blades 4-4′. In this embodiment according to the invention, the rotor blades 4-4′ (see FIG. 2 a and FIG. 2 b) are embodied as a thin, flat plate. More specifically, the plate-shaped rotor blades are furthermore flexible as regards its shape, so that they will automatically assume their desired shape, owing to the occurrence of centrifugal forces, during rotation of the horizontal shaft 3. Said shape, also called chain line, ensures that only tensile stress will occur in the rotor blade and that consequently the stress at the two ends 3 a and 3 b, respectively, of the shaft 3 will be minimal, which enables a further simplification of the construction.

FIGS. 3 a and 3 b show another embodiment of the invention. This embodiment makes use of rotor blades 4″-4′″ of different shape, which rotor blades are likewise mounted on the horizontal shaft 3 with their first and second ends. More specifically, the rotor blades 4″-4′″are provided with additional wind capturing means 5, which preferably consist of a widened portion of the rotor blade 4″-4′″.

In a specific embodiment, the widened portion of the rotor blade, which functions as a wind capturing means, is circular in shape; in the embodiment that is shown in FIGS. 3 a-3 b, the widened portion of each rotor blade 4″-4′″ functioning as a wind capturing means 5 is ellipsoidal in shape. The first main shaft 6 of the ellipsoidal wind capturing means 5 may thereby coincide with the longitudinal axis 7 of the rotor blade 4″; however, in order to obtain a strongly improved efficiency of the wind energy conversion apparatus, the first main shaft 6 includes an angle α with the longitudinal axis 7 of the rotor blade, which angle preferably ranges between 0° and 60°, more in particular between 20° and 40°.

As FIG. 3 b shows, the widened portion 5 that functions as a wind capturing means does not form an ellipsoid in a geometric sense, but the ellipsoid 5 more or less smoothly merges with the outer circumference of the strip-shaped rotor or blade 4′″.

As a result of a suitable integration of the wind capturing means 5 in each rotor blade (seen in the wind direction V_(wind)), any segment dS moves along the path described by the circumferential surface of a truncated cone, as is shown in FIG. 4, wherein the plane of inflow 9 of the wind capturing means S intersects the horizontal shaft 3 at an upstream position 30, seen in the direction of the oncoming wind V_(wind). During rotation of the rotor blades by the oncoming wind V_(wind), the wind reaction force 15 of the rotor 4′″ extends perpendicularly to the plane of inflow 9 of the wind capturing means 5. Said force 15 can be resolved into a force 16 acting in a direction parallel to the horizontal shaft 3 and a force 17 acting in the radial plane of the supporting structure.

Said radial force 17 will create an underpressure in the region 18 surrounding the horizontal shaft 3, and furthermore said force 17 will carry air radially outwards downstream thereof, as is indicated by the arrow 19. As a result of the presence of the underpressure in the region 38, the air flow will contract, causing the mass flow of the air through the entire apparatus and through the area of the rotors 4′ to increase. This in turn results in more energy being drawn from the air flow, which leads to a significantly improved efficiency of such wind energy conversion apparatuses.

The aforesaid effect of contraction of the oncoming air through the rotating rotor blades 4′″ can be compared with the phenomenon that occurs in the converging portion of a Venturi tube.

As a result of the inclined position of the wind capturing means 5 on the rotor blades 4′″. a conical surface 20 is covered during rotation, which acts as the throat or constriction of Venturi tubes.

More in particular, the rotor blades according to the invention may be made of a metal or of a plastic material,

Although two rotor blades 4-4′ are mounted on the horizontal shaft 3 in FIG. 1, is also possible to use only one rotor blade. It is also possible, on the other hand, to use more than two rotor blades, and in the situation in which several rotor blades are mounted on the same horizontal shaft, said rotor blades may have mutually different radii. The wind energy conversion apparatus according to the invention is characterized by a simple and light construction, which makes the wind energy conversion very suitable for use in areas not covered by the electricity grid.

Since only tensile stress, no flexural stress, occurs in the rotor blade, the wind energy conversion apparatuses is characterized by its light and simple construction. Since the aerodynamic angle of incidence of the wind V_(wind) is furthermore constant (or at least not variable), and an actual rotor blade tip is missing, the wind energy conversion apparatus according to the invention is characterized by a very low noise level. This latter characteristic makes it possible to install the apparatus in built-up areas, whereas the noise level during operation of the wind energy conversion apparatuses that are currently known is generally too high to make installation thereof in built-up areas feasible. 

1-22. (canceled)
 23. A wind energy conversion apparatus comprising: a supporting structure; a horizontal shaft having a first and a second end, which is rotatably journalled in said supporting structure; as well as at least one rotor blade having a first end and a second end, which rotor blade is mounted on said shaft with both ends, characterized in that the rotor blade is provided with additional wind capturing means.
 24. The wind energy conversion apparatus according to 23, characterized in that said wind capturing means consist of a widened portion of the rotor blade.
 25. The wind energy conversion apparatus according to 24, characterized in that said widened portion is circular in shape.
 26. The wind energy conversion apparatus according to 24, characterized in that said widened portion is ellipsoidal in shape.
 27. The wind energy conversion apparatus according to 23, characterized in that the rotor blade is elongate in shape.
 28. The wind energy conversion apparatus according to 27, characterized in that the rotor blade is a thin, flat plate.
 29. The wind energy conversion apparatus according to 23, characterized in that the rotor blade is made of a metal.
 30. The wind energy conversion apparatus according to 23, characterized in that the rotor blade is made of a plastic material.
 31. The wind energy conversion apparatus according to 23, characterized in that the apparatus comprises two or more rotor blades mounted on said shaft.
 32. The wind energy conversion apparatus according to 31, characterized in that the rotor blades describe different diameters during operation.
 33. The wind energy conversion apparatus according to 23, characterized in that the shaft is mounted in bearings in the supporting structure with both its ends.
 34. The wind energy conversion apparatus according to 23, characterized in that the shaft is coupled with means, such as a generator, for converting rotational energy into electrical energy.
 35. The wind energy conversion apparatus according to 23, characterized in that said generator is mounted in or on said bearing-mounted shaft.
 36. The wind energy conversion apparatus according to 23, further comprising a mast construction on which at least two rotors are mounted.
 37. The rotor blade intended for being mounted on a wind energy conversion apparatus according to 23, wherein the rotor blade can be mounted on a rotatable horizontal shaft of the wind energy conversion apparatus with both its ends, characterized in that said rotor blade is provided with additional wind capturing means.
 38. The rotor blade according to 37, characterized in that said wind capturing means consist of a widened portion of the rotor blade.
 39. The rotor blade according to 38, characterized in that said widened portion is circular in shape.
 40. The rotor blade according to 38, characterized in that said widened portion is ellipsoidal in shape.
 41. The rotor blade according to 37, characterized in that the rotor blade is elongate in shape.
 42. The rotor blade according to 41, characterized in that the rotor blade is a thin, flat plate.
 43. The rotor blade according to 37, characterized in that the rotor blade is made of a metal.
 44. The rotor blade according to 37, characterized in that the rotor blade is made of a plastic material. 